Electrophotographic (“EPG”) printing involves the use of an image carrying member that is initially charged to a substantially uniform potential. An electrostatic latent image is formed on the photoconductor, usually by way of a light source, which discharges the charged photoconductor in selected areas. The latent image is then transferred by bringing a developer material, typically a toner, into contact with the photoconductor surface. The developed image is then transferred to a recording sheet (e.g. paper sheet, transparency sheet) and permanently affixed thereto by fusing with applied heat and pressure.
An encoded strip provides a solution to the known motion control problems when using an organic photoconductor “OPC” belt in an EPG apparatus. Imaging systems require the OPC belt to move and/or rotate within the system and require the movement or motion quality to be very accurate and free from vibrations or slips. A belt does not provide a stable surface when rotating around a plurality of rollers. The belt will laterally shift in one direction or another. This shift causes poor image quality. This problem is exaggerated in a tone-on-tone EPG developing system where accuracy is very important when placing a particle of toner, which is about 12 microns in diameter on top of another particle of toner, which is also about 12 microns in diameter. The present invention solves the problem of shifting of a belt in a tone-on-tone EPG developing system by placing a thin printed strip which could be printed directly onto the belt or printed on tape which adheres to the belt and mounting an optical sensor in a close relation to the strip. Thus, if an OPC belt does slip or become misaligned, the imaging system's controller will be able to compensate for the error by shifting key set points in the imaging system. The photoconductor can be comprised of a drum or belt, which is made of an organic material. One purpose of the present invention is to provide a solution to the known problem of securing material to an organic photoconductor (“OPC”) belt material in an automated manufacturing environment. Usually, material is applied to an OPC belt by hand. Hand application of strip material is time-consuming, costly, and prone to inaccurate placement on the OPC belt. The extra time taken to apply the strip material by hand increase the OPC belt's exposure to light, which can damage the OPC material. Furthermore, pulling the strip by hand can deform the strip because of excessive force used to pull the strip before application. Thus using an automated, controlled process to apply material minimizes damage to the belt and strip, resulting in higher yield of belts and strips per spool. Accordingly, it is an object of the present invention to provide a low cost, practical, and efficient manner of adhering a continuous encoder strip (“code strip”) to achieve a desired print registration for printers, copiers, input scanners, and other related machines.
Thus, when the belt shifts, the pattern will also shift. When the pattern shifts, the sensor will read the shift and inform the controller of the EPG developing system to shift the light source to compensate for the misalignment (“misregistration”).
The use of a code strip and a sensor, shown in FIG. 5, enables supplying the system's controller with the exact location of the OPC belt. Placing a pattern, shown in FIGS. 3A and 3B, on the code strip, that can show two variables, the X-direction and the Y-direction and using an algorithm to define the exact location of the OPC belt.
The present invention relates to the art of encoding the movement of an OPC belt. Imaging devices require that the image transferred onto the OPC be registered accurately with the image light source. A code strip helps establish the position of a marking or sensing device mounted for exposing across a printing medium on which an image is to be printed, or from which an image is to be read.
A code strip is a graduated strip, generally disposed across an area where the medium is held, and having gradations that can be automatically sensed. Historically code strips have been made of polymer material with fiduciary markings formed photographically. For optimum performance, the code strip's fiduciary markings should be very close to both a light source and a detector used as parts of a sensing system for reading the fiduciary markings.
A code strip obviates the need for an encoder wheel or roller, as the strip rides along with the OPC belt in concert with the belt's motion. Instead of using a large diameter roller, a thin strip attached or printed to the belt surface occupies negligible space in the printer architecture. Without an encoder roller, the two greatest contributions to misregistration, roller runout and eccentricity, disappear. The space saved can be used by other hardware. Color systems require substantial hardware space for multiple development stations, erase stations, charging stations, and light sources. Multiple pass systems require the OPC belt to revolve several times. Each cycle can multiply the effects from roller tolerances. Using a code strip that moves with the belt provides more accurate data about the belt motion.